TBI 350 barely runs after tbi rebuild

[iamtherealJayy]

So I finally got around to showing my original truck some love, and as always it has fought me every step of the way. I got the throttle body out cleaned up all new gaskets etc. I took the tps and iac out to clean it. Got everything back on and assembled, truck fired instantly and idle I let it warm up to reset the iac, shut teuck off jumped a and b on aldl ignition on wait ten seconds unplug iac turn ign off and remove jumper. This is around where the issue started, I had to give it some throttle to get it to start after this. I got the tps set at .58V at closed throttle. I can rev the engine from the throttle linkage and it returns to idle, I can then press it closed a little bit more and it will stall the engine. It also cranks for around 12 seconds now.
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https://youtube.com/shorts/GhZpcS55pQs?feature=share
Did I somehow reset the iac completely wrong? It just doesn’t make sense how cleaning it and resealing all the leaky parts made it so much worse.

 

[gmbellew]

iac can't really be "cleaned" except foe just the pintle. if you squirted stuff inside it, it could be getting lazy.

 

[iamtherealJayy]

The iac is new was replaced last year ish, I removed it and the throttle position sensor to clean the throttle body. The iac looked brand new. I haven’t put maybe 1000 miles since install.
Edit: nothing was sprayed on, in, around, above, anything to do with the iac or tps. All I did was replace the iac gasket and set tps to .58V and attempt to reset iac since I had it all apart.

 

[gmbellew]

if the IAC is unplugged with it closed, the throttle cannot be forced closed completely or the engine will die bc it has no air. with IAC closed, set the throttle screw to be about 100rpm less than target (see GM manual of running a stock computer) at warm idle. then turn off truck and plug in IAC. then start truck and you should be good.

alternatively if you have a data stream from a cable, you can keep adjusting the throttle screw, starting and idling truck with IAC hooked up to get the IAC counts in the 10-30 range, and then adjust TPS to be around .5-.7v after IAC is good.

 

[iamtherealJayy]

The throttle screw is still capped off, if possible I’d like to avoid breaking the cap out. Could I do that procedure and just leave the idle wherever it’s at

 

[iamtherealJayy]

This morning I drove to the gas station got some breakfast went to leave and the truck stalled, started back up drove home. Ate breakfast tried to go to work, stalled going down the driveway then just starts and stalls and won’t stay running, with throttle I can keep it alive, I put it in reverse started it and took off back up the driveway and got in something else and went to work.

 

[iamtherealJayy]

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This is all I’m getting today

 

[Bextreme04]

I'm really confused. You said you reset the IAC.. but you only did half the procedure? Why would you not want to adjust your idle screw? You are obviously having an issue with the idle set screw position.

You need to do the warm up, short A and B, turn key on for 10 seconds, then unplug the IAC and start the truck. Once its running you HAVE to set the idle to about 100 less than desired. The desired is usually ~750rpm for most of the truck engines, so you need to set the idle screw to keep the truck at 650rpm with the IAC valve closed and unplugged. That puts the throttle in the right position for the IAC to be able top control it. Once it is idling at 650rpm with IAC unplugged, turn off the truck and plug the IAC back in. NOW you have reset the IAC.

 

[iamtherealJayy]

I assumed it had to be set since it had been removed. I’ve replaced the iac before(my first thread) and I never had to remove the screw cap

 

[gmbellew]

have you ever reconnected rhe IAC harness? the original post never says you reconnected it. if it is disconnected, you are choking the air down and that is why it is stalling.

also, if you can manipulate the throttle more "closed" past the resting position, maybe check the throttle blade shaft bushings for play?

 

[iamtherealJayy]

Yes iac was reconnected. The butterfly’s in the Venturi have a stiff spot. It’s not super noticeable doing it by hand but that’s the reason I originally rebuild the tb other than it was leaking around the regulator? I believe. Where it returns to on its own isn’t stiff but if the throttle snaps closed it goes to where it would if I pulled it closed a little more and then the pedal is hard to press until it “breaks free” if that makes any sense.

 

[gmbellew]

Yes iac was reconnected. The butterfly’s in the Venturi have a stiff spot. It’s not super noticeable doing it by hand but that’s the reason I originally rebuild the tb other than it was leaking around the regulator? I believe. Where it returns to on its own isn’t stiff but if the throttle snaps closed it goes to where it would if I pulled it closed a little more and then the pedal is hard to press until it “breaks free” if that makes any sense.

sounds like that may be the issue...if it closes too quick and gets stuck, the IAC may not be able to open fast enough to catch it or closes too much because it is expecting more air past the throttle blades.

I'd pop that plug and turn the screw a 1/4 turn clockwise. see if that helps it not get stuck.

 

[squaredeal91]

On the underhood video with air cleaner off, I can't tell in the video but can you tell me if when the engine dies does it keep spraying with rpms or does it cut out?

 

[iamtherealJayy]

As the idle surges the spray pattern fluctuates with rpm. When the engine dies it stops spraying.

 

[squaredeal91]

Sounds like it's dying because it stops spraying and not losing spark. Possibly pickup coil. It's hard to see it with distributor in the rig and there covered by the shaft, but they usually start to turn green from the copper corrosion.